Modern semi-permanent continuous-flow left ventricular assist devices (LVADs) are cost-effective and durable surgically-implanted mechanical devices which augment or substitute for a poorly functioning or nonfunctioning diseased left ventricle of the heart to maintain blood circulation to the body. LVADs are now considered to be a reasonable alternative to orthotopic heart transplantation, especially given the severe shortage of suitable donor organs. Continuous-flow LVADs have replaced earlier pulsatile models because they are more durable, less cumbersome, and have been shown to increase survival, exercise capacity and quality of life. LVADs are used to sustain patients with advanced congestive heart failure (CHF) who cannot be managed medically either as a bridge-to-heart transplantation, as destination therapy or, in those patients whose CHF is deemed at least partially reversible, as a bridge-to-recovery. The frequency of sufficient recovery to permit LVAD explantation is estimated to be 10-20% in CHF of non-ischemic etiology and in <1% in ischemic CHF. LVAD implantation is generally indicated in CHF when cardiac index (CI) is <2 L/min/m2, systemic systolic arterial pressure is <90 mm Hg, left atrial pressure is >20 mm Hg, or the systemic vascular resistance is >1.57 mm Hg/mL. Advances in the durability and miniaturization of LVADs, afforded by continuous-flow rather than pulsatile design, have enabled more extensive and longer-duration utilization.
Unfortunately, failure of the right ventricle has been reported in 15% of continuous-flow LVAD recipients within the first 30 days following implantation and in 20-50% of LVAD recipients overall. As such, right ventricular failure remains a major limitation of LVAD utility, and is associated with markedly poorer prognosis.
Furthermore, continuous-flow LVADs generate reduced pulsatility of peripheral perfusion compared to pulsatile-flow LVAD devices and/or the normal circulation derived from a well-functioning human heart as measured by pulsatility index, pulse pressure and/or the frequency of opening of the aortic valve, and this reduced pulsatility has been implicated in a number of adverse events including reduced peripheral vascular compliance, gastrointestinal bleeding, arteriovenous malformations, hemolysis, pump thrombosis, aortic insufficiency and lower rate of recovery of left ventricular function.
Accordingly, there is a need for adjunctive therapies that enhance the use of LVADs and/or reduce the risk of right ventricular failure associated with LVADs and/or reduce the risk of other LVAD-related adverse events.